JPS60124366A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE:To preheat supplementing water to the same temperature as that of a cell and keep the temperature of electrolyte constant and decrease variation of power generating output of a fuel cell by using reaction gas, which is the same temperature as that of a cell, coming from a cell main body as a heat source used to preheat supplementing water. CONSTITUTION:An oxidizing gas supply line 40 sucks air A from the outside with a blower 41 and supplies it to an oxidizing gas chamber 14 of a cell main chamber 10. The air exhausted from the oxidizing gas chamber enters a condenser 42 through a heat exchange tube with fins 53a of a preheating bath 53 in a supplementing water supply line 50 and is cooled by cooling water W which flows inside a cooling pipe with fins 42a, and reaction product moisture contained in the air is condensed. The part of air from the condenser is discharged to atmosphere At, but the rest is sucked to the blower and circulated to the cell main body.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a power generation device using a free electrolyte type fuel cell.

[Prior art and its problems]

The free electrolyte fuel cell described above is suitable for a low-temperature operation type fuel cell that uses an alkaline aqueous solution such as caustic potash as an electrolyte, hydrogen as a fuel gas, and air or oxygen as an oxidizing gas. In addition to the fuel cell main body, a power generation device using this type of fuel cell is equipped with a circulation system for circulating an electrolytic solution and a reaction gas supply system for supplying fuel gas and oxidizing gas. In addition to the above-mentioned liquid circulation and gas supply, the functions of the system include the removal of the amount of heat generated in the battery body as a result of power generation and the water produced by the reaction. It is advantageous to take out the generation during battery operation, Ml:. Indeed, this method has the great advantage that it can also be used to remove reaction product water that occurs within the battery as a result of power generation.

FIG. 1 is a system diagram showing the configuration of a fuel cell power generation apparatus using such a means, in which a fuel cell main body 1° is connected to a fuel gas chamber j3 and an oxidizing gas chamber 14 by a fuel gas electrode 11 and an oxidizing gas electrode 12. It is schematically shown as a frame partitioned into three chambers, ie, an electrolyte chamber 15 and an electrolyte chamber 15. The electrolyte circulation system 2o includes an electrolyte reservoir 21 and an electrolyte pump 22, and allows the electrolyte E to flow into the electrolyte chamber 15. A fuel gas supply system 30 in the reaction gas supply system sends a fuel gas F, for example, hydrogen, from a fuel gas source (not shown) on the left side of the figure to a fuel gas chamber 13 in the cell via an ejector 31, and from the fuel gas chamber 13. The fuel gas exiting the battery is sucked into the ejector 31 described above via the condenser 32 and sent to the battery again.

In this way, the fuel gas supply system 3o is configured as a gas supply and circulation system that allows several times the consumption amount of fuel gas to flow into the fuel gas chamber 13, and the sensible heat generated in the battery is It is carried away by the cooling water W.

The oxidizing gas supply system 40, which is the other reactive gas supply system, sucks air A as an oxidizing gas from the left side of the figure into a blower 41 and supplies it to the oxidizing gas chamber 14 in the battery main body 10.

In this case, since the air A effectively contains only about 20% oxygen as an oxidizing gas, the entire amount is not consumed within the fuel cell main body 10, and the remaining nitrogen that does not participate in the reaction is consumed. The remaining oxygen leaves the battery and is discharged to the atmosphere via the condenser 42. However, in this case, there is no need to use a condenser to condense the moisture contained in the exhaust air. It may also be released into the atmosphere.

Now, in the above-mentioned system, the calorific value generated within the battery body and the water produced by the reaction are taken out of the battery in the form of water vapor that evaporates into the reaction gas, so the necessary amount of heat and generated amount can be obtained. It cannot always be removed in an equilibrium manner, and under normal battery operating conditions, it is possible to remove the necessary area from the battery. It will end up being put away.

Therefore, if left as is, the concentration of the electrolytic solution will become higher than the specified value, so it is necessary to add makeup water to the electrolytic solution.

The make-up water supply system 5o in FIG. It is supplied to the electrolyte reservoir 21 in the electrolyte circulation system 2°1. Incidentally, condensed water exceeding a predetermined amount exceeding the overflow portion 51b and the water surface 51a is discharged into the condensed water reservoir 51.

However, the fuel cell power generating apparatus configured as described above has a drawback in that the battery output fluctuates over time, and it has been found that the main cause of this is the above-mentioned make-up water supply system. That is, the temperature of the condensed water condensed in the condensers 32 and 42 is lower than the operating temperature of the battery due to the cooling water W, and this relatively low temperature condensed water C is transferred from the condensed water reservoir 51 to the make-up water pump 52. When water is supplied to the electrolyte reservoir 21 as make-up water, the electrolyte temperature T in the electrolyte reservoir is approximately 10° C., as shown in (a) of the actual measurement results shown in FIG. In the same figure (a+, the horizontal axis is time (minutes) and the vertical axis is the electrolyte temperature T.
The time ts is the start of supply of makeup water, and the time ts is the end of supply. The fluctuation in the battery output P due to such a temporary drop in the electrolyte temperature is unexpectedly large, as shown in FIG. 2(b), and it takes more than 10 minutes to return to the end of the supply of makeup water.

Water can be supplied continuously, but if too much make-up water is added to the electrolyte, the concentration will drop and this will affect the battery output, so it is better to supply make-up water intermittently for operational reasons.

In addition, if the temperature of the cooling water W is raised, the condensed water temperature and therefore the make-up water temperature can be raised, but moisture condensation from the reaction gas, especially the fuel gas, becomes insufficient, and moist fuel gas is supplied to the battery body. As a result, the function of the electrode may be impaired. This is because if the gas diffusivity of the electrode becomes poor due to moisture in the fuel gas, the power generation effect of the electrode will be reduced.

[Purpose of the invention]

In view of the above-mentioned drawbacks of the conventional devices, the present invention configures a fuel cell power generation device so that the supply of make-up water to the electrolyte circulation system has little effect on the output of the battery and stable output can be obtained. The purpose is to

[Key points of the invention]

An electrolytic solution circulation system that circulates an electrolytic solution through the body, a reactive gas supply system that supplies reactive gas to the battery/cell water body and causes it to flow within the body, and reaction product water that is discharged from the battery body by the reactive gas supply system. a make-up water supply system that supplies make-up water to the electrolyte reservoir in an amount corresponding to the excess discharge amount; This is achieved by constructing a heat exchanger that heats to the same temperature as the discharge temperature from the main body.

[Embodiments of the invention] The present invention will be described in detail below with reference to the drawings.

FIG. 3 is a system diagram showing the first embodiment of the present invention, in which the same parts as in FIG. In order to emphasize this, the fuel gas supply system is omitted from this figure. The circulation system 20 is not much different from that shown in FIG. 1, but an electrode-type liquid level detector 21b is shown in the electrolytic solution reservoir 21 to detect the liquid level 21a. 21b emits a detection signal when the liquid level 21a comes to the tips of the left and right electrode legs extending downward in the figure, and this starts and stops the make-up water pump 52 of the make-up water supply system 50 to lower the liquid level 21a. By controlling the amount of electrolyte E within a relatively small range, the amount of electrolyte E in the electrolyte reservoir 21 is adjusted to a constant value, and the total amount of electrolyte in the electrolyte circulation system is thereby kept constant. The concentration of the electrolyte sent to the electrolyte chamber 15 of the main body 10 is maintained at a predetermined value.The tip of the electrolyte return pipe from the electrolyte chamber 15 to the electrolyte reservoir 21 is placed directly above the electrolyte surface 21a. It is open, so even if a small amount of reactive gas is mixed into the electrolyte inside the battery,
At this point, the air is separated from the liquid and sent to the oxidizing gas chamber 14 where it is diffused into the atmosphere.The air discharged from the oxidizing gas chamber 14 to the outside of the battery body is fed to a preheating tank 5 added to the make-up water supply system 50.
3 through the finned heat exchange tube 53a to the condenser 42.
The finned cooling pipe 42a is cooled by the flowing cooling water W, and the water produced by the reaction contained therein is condensed. Part of the air that leaves the condenser becomes atmospheric At
However, a significant portion of the remainder is discharged to the blower 41 again.
is sucked into the battery and recirculated to the battery body. By using a circulation system as the oxidizing gas supply system as in this embodiment, the blower 4
A larger amount of air than the air that the cell 1 draws in from the atmosphere is passed through the oxidizing gas chamber 14, and the amount of heat generated within the battery body is sufficiently removed and transferred to the cooling water W within the condenser 42. The same applies to the removal of reaction product water, and by increasing the amount of air flowing through the oxidizing gas chamber 14, the oxidizing gas supply system alone or together with the fuel gas supply system can be removed within the battery main body 10. A larger amount of reaction-produced water than is produced is removed from the electrolyte in the battery body 10, and the battery is operated in a state where the gas diffusivity of the electrodes is sufficient.

In this way, the reaction gas supply system prevents reaction product water from being released. As this make-up water, it is desirable to use the condensed water C with a little impurity in the condenser 42 as in the past, and for this reason, the condensed water C is poured from the bottom of the condenser 421 into the condensed water shown in the lower right of the figure. The water is led to the water reservoir 51, and a certain amount is stored by adjusting the level of the overflow 51b. The above-mentioned preheating tanks 53 are installed side by side on the side of the condensed water reservoir 51, and the condensed water reservoirs of both are in communication, so that the liquid level 53b in the preheating tank 53 is also equal to that of the condensed water reservoir 51. A predetermined amount of condensed water is stored as much as the liquid level 51a. The condensed water in the preheating tank 53 is heated by the air heated by the battery body 10 flowing in the heat exchange tube 53a, and since the temperature is substantially the same as the operating temperature of the battery, the condensed water is also heated. It is heated to the same temperature as the battery's operating temperature. Of course, from the battery body 10 to the preheating tank 5
It is desirable that the air piping leading to No. 3 be covered with thermal insulation to prevent heat from escaping to the outside air. The condensed water in the preheating tank 53, which has been preheated to the battery temperature in this way, and the electrolyte reservoir 21 described above
The replenishment water bottle is turned on in response to a command from the liquid level detector 21b. As can be seen from Figure (a), the temperature T of the electrolytic solution in the electrolytic solution reservoir decreased compared to the conventional method, and the actual measured value was about 3°C. Correspondingly, the fluctuations in the battery output P shown in FIG. , 5
It was about %. However, this result shows that the temperature of the condensed water preheated in the preheating tank 53 is about 10°C compared to the battery temperature of 60°C.
This is a value that can be improved by preheating the battery at a low temperature of 50°C, but even so, the value of the 1st and 5th coefficients of variation in battery output is still low due to the I + Gema 1++1/r profit p1 8 1 color song positive squid, input - → ax lran f>As you can see, the time from when the electrolyte temperature T and battery output P decrease by -tan until they return to normal values. has also decreased significantly.

FIG. 5 is a system diagram showing a second embodiment of the present invention. In this figure, except that the fuel gas supply system 3o is shown, the same parts as in the previous FIG. 3 are given the same reference numerals. This embodiment differs from the previous embodiment in that it is used as a medium for heating the condensed water C in the preheating tank 53, rather than the condenser 32 of the fuel gas supply system 3o and the oxidizing gas system. There are many advantages. It is inevitable that the temperature of the cooling water will be lower than the reaction gas discharged from the battery main body 10, but in the '4 condenser, the mizuna mood that was rare in the reaction gas will condense. Since a large amount of sensible heat is generated, the condenser outlet temperature of the cooling water warmed by this is not much different from the reactant gas inlet temperature. Further, in order to prevent the amount of preheating heat from being insufficient, cooling water from two condensers 32 and 42 can be introduced into the preheating tank 53 as shown in the figure.

Both of the above-mentioned art collection systems use reactive gas that comes out of the battery body and has the same temperature as the batteries as a heat source to preheat the make-up water, so the make-up water is preheated to almost the same temperature as the batteries, which prevents excessive preheating. There is no needless fluctuation in the temperature of the stain remover due to shortage, and the system in which the present invention is implemented operates extremely stably. Well, the reactant gas supply system sends reactant gas to the main body of the pond at a flow rate that is sufficient to discharge water in excess of the reaction product water to the outside of the battery, so it is heated enough to heat up the make-up water. Since the point at which the amount of reaction gas is obtained is heated to approximately the same temperature, the temperature of the electrolyte that is circulated to the battery fluctuates due to the supply of make-up water is much less than before. The power generation output of the fuel cell hardly fluctuates.

The system of the fuel cell power generation apparatus according to the present invention is essentially stable as described above, and there is no risk of fluctuations within the system due to excessive control or adjustment, and operation can be continued with peace of mind. Furthermore, accompanying the above, the total liquid volume control of the electrolyte circulation system, and therefore the concentration control of the electrolyte, is also highly reliable, and this is compatible with the fact that the gas diffusivity of the electrode is maintained under good conditions by the reaction gas supply system. In this way, it is possible to guarantee that the fuel cell power generation device can be operated with high efficiency for a long period of time.

[Brief explanation of the drawing]

Figure 1 is a system diagram showing the configuration of a conventional fuel cell power generation device.
Figure 2 is a graph showing the operating results of the conventional device;
The figure is a system diagram showing the configuration of the first embodiment of the fuel cell device according to the present invention, FIG. vessel,
30: Fuel gas supply system as a reaction gas supply system, 32.
42: Condenser that condenses the water produced by the reaction, 40: Reaction gas? Oxidizing gas supply system as a supply system, 50: Makeup water, primary supply system, 53: Makeup water preheating tank, 53a, 53C: Fined heat exchange tube as heat exchange means, A: Air as reaction gas, C : Condensed water used as make-up water, E
: electrolyte, F: fuel gas as reaction gas. j-'fit special license key river 1] 1st figure 51 P 3rd figure

Claims (1)

[Scope of Claims] 1) A fuel cell that includes a fuel cell main body through which an electrolytic solution is passed and generates electricity by receiving a reaction gas supply, and an electrolytic solution reservoir that adjusts the total amount of electrolytic solution to a constant level; An electrolyte circulation system that circulates the electrolyte through the main body, a reaction gas supply system that causes the electrolyte to flow, and make-up water that corresponds to the excess discharge of reaction product water discharged from the battery main body. into the electrolyte reservoir! a make-up water supply system for supplying the electrolyte; and a heat exchange means for heating the make-up water supplied to the electrolyte reservoir to the same temperature as the discharge temperature of the reactant gas from the battery main body by the amount of heat taken out from the battery main body together with the reactant gas. Fuel cell power generation equipment. 2. A fuel cell power generation device characterized in that it is a make-up water thermal tank that directly exchanges heat with make-up water in the power generation device according to claim 1. 3) In the power generation device according to claim 1, the reaction gas supply system includes a condenser that cools the reaction gas with cooling water and condenses reaction product water discharged from the battery body together with the reaction gas. 1. A fuel cell power generation device, wherein the heat exchange means is a make-up water thermal tank that exchanges heat between the outlet-side cooling water from the condenser and make-up water. 4) A fuel cell power generating apparatus according to claim 3, in which the reaction product -'hl is condensed in the condenser as make-up water. /